Process of making screens for color photography.



'ject of the Emperor of UNITED STATES PA'IENT OFFICE,

oAnL srarn, or s'rricm'rz, NEAR BEnLiN, GERMANY, assrsnoa r0 ACTIENGESELL- scrrar'r rim ANALIN FABRIKATION, or BERLIN, GERMANY.

PROCESS OF MAKING SCREENS FOR COLOR- PHOTOGRAPHY.

Specification of Letters Patent.

Patented J an. 11, 1910.

No Drawing. Original application filed March ,17, I909, Serial No.484,028. Divided and this application filed October 2, 1909. Serial No.520,695. i

To all whom it my concern:

Be it known that I, CARL SPATH, a sub- Germany, residing at Steglitz,near Berlin, Germany, have invented certain new and useful Improvementsin Processes of Making Screens for Color Photography, of'which thefollowing is a specification.

My invention relates to a new kind of screens for color photography madefrom chromated gelatin, wh ch is essentially characterized by the factthat the colors are distributed in one single la er of elatin and thatthe small lines and gures h lled by the different colors aresymmetrically arranged. In the manufacture of such screens which hasrecently become known, advantage is taken of the fact that certaindye-stuffs will dye gelatin which has been treated with bichromate andex osed to light, in preference to elatin which has not been so treated,whl e other dye'stufl's will dye the unaltered elatin in preference tothe treated gelatin.

f, therefore, a chromated layer of gelatin be ex osed to light'beneath ascreen ruled with lack linescommonly called a blackwhite screenandsubsequently washed to remove bichromate, a two color screen can beprepared b dyeing the layer with appropriate dyestu s. In order toobtain such a new screen I proceed as follows, the recess beinperformedin two steps, the rst of whic consists in making a two-colorscreen 1n 0. layer of chromated gelatin, which twocolor screen is,transformed in the second ste into a three-color screen.

or the first step of the process I give the following example: A lassplate, or a fiat film of celluloid, or the like, is coated with athlnlayer of gelatin and the gelatin sensitized in the usual way bymeans of potasslum bichromate; the plate thus reparcd is exposed to lilit under a black-w ite screen of about'20 ines per millimeter obtainingthus a set of lines 1n the elatin alternately altered and unalteredbyline action of light, whereupon the excess of the bichromate is washedout. The plate is then immersed in a dyeing solution containing a redand a green dyestuif, the red dyestufi having afmt for the alteredgelatin and the green one or the unaltered gelatin. As such a red tinlayer for dyestulf I may use azo-rubin and ponceau in crystals (S oranother suitable dyestuif as a green dyestufi' adapted for my presentprocess I name for instance naphtholgreen. By immersing the plate insuch a two-colored solution and then washing out the excess of thedyestuff a red-green screen is obtained. After this first step the plateis sensitized with potassium bichromate for a second time and thenexposed to light under the blackwhite screen turned to a suitable angle,whereupon the plate is washed with water eliminating the excess ofbichromate and the green dyestuff also from the small quadran larelements not altered by the action of light. Now the plate is dyed in ablue solution containing for instance, methyl blue, brilliant blue forwool G and brilliant azurine which have only affinity for the unalteredgelatin. After having washed out the excess of the green dye thereresults therefore a red-green-blue three-color screen, which, in thesame manner as the screen produced above shows in a symmetricalarrangement green and blue quadrangular elements between red lines.

It is obvious to those skilled in the art that my present invention isnot limited to the foregoin example or to the details given therein, asor instance to the succession of the dyestuffs employed in my process,etc.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

A rocess of makin a three-color screen whic1 consists in div ding a thinlayer of chromated elatin by exposure to light under a black-whitescreen into a set of lines alternately altered and unaltered by theaction of light, removing the excess of bichromate, dyeing theso-prepared gelatin with two colors in a solution of two dyestufls, oneof which is adapted to dye only the gelatin altered by the action oflight, and the other to dye only the unaltered elatin, washing out theexcess of dye, sensltizing the gelaa second time with bichromate,exposing to light under the same black-white screen but the linescrossing the lines of the first exposure at a suitable angle, washingthe gelatin to remove the excess of bichromate as well as of thedyestufi', which has aflinity only for the unaltered gelatin, from thesmaller quadrangular elements of unaltered gelatin produced by thesecond exposure to light and then dyeing these decolorized smallelements with a third dyestuff having the property to dye only theunaltered gelatin.

In testimony whereof I have hereunto set my hand in presence of twosubscribing witnesses.

- CARL SPATH. Witnesses:

WOLDEMAB HAUPT, HENRY HASPER.

